A color liquid crystal display device is one of typical electronic devices. The structure of the display device will be explained as an example. In the device, a color filter is provided on one side of a liquid crystal layer. A printing method can be used to manufacture the color filter. In this method, color inks dispersed pigments in a resin solvent are printed on a transparent glass substrate in the shape of dots or stripes. This method is suitable for lowering the required cost and increasing the mass productivity.
Specifically, in the printing method, color inks, red (R), green (G), and blue (B), are printed on a glass substrate in the shape of a desired pattern, by means of a gravure offset printing system equipped with a blanket of a cylinder press type. FIG. 1 is a cross sectional view of a color filter obtained after printing and drying treatments. As can be understood from FIG. 1, first, a light-insulation black layer BM is formed on a glass substrate 21 in the shape of a matrix. Then, a stripe of a red ink layer R is printed in one of the regions in which the black layer BM is not formed substantially, by rotating the cylinder press-type transfer blanket and moving the same from the to the in the figure. Subsequently, a green ink layer G is printed in that region located adjacent to the region coated with the red ink layer R which is not coated with the black layer BM substantially, and then a blue ink layer B is printed in a manner similar to the above. As is shown in FIG. 1, the surface of each of the three color ink layers is arcuate in a state in which the layers are printed on the glass substrate. In other words, the thickness of each color ink layer is minimum at its both opposite boundary regions, and maximum at its central region.
In this state, unevenness in color may be caused, and therefore a color liquid crystal display of high quality cannot be obtained. Thus, it is necessary to make smooth the surface of each color ink layer. Various methods of smoothing the uneven surfaces of resin layers have been proposed. As one of those methods, a method of smoothing the surfaces of color ink layers by means of a wrapping film having fine particles is known from Published Unexamined Japanese Patent Application No. 61-3122. Further, according to another method as disclosed in Published Unexamined Japanese Patent Applications Nos. 63-216028 and 1-167807, the convex portions of color ink layers are heated and then smoothed by pressing with the use of a rubber or a planished metal roller. Moreover, Published Unexamined Japanese Patent Applications Nos. 2-251816 and 62-280805 disclose a method of smoothing color ink layers formed on the glass substrate of a color filter, by bringing the layers into contact with a flat plate or a machine plate, directly or with a releasable film interposed therebetween, and pressing by the use of a press roller or the machine platen from the side of the glass substrate.
Specifically, in the method disclosed in Published Unexamined Japanese Patent Application No. 62-280805, as is shown in FIG. 2, color ink layers R, G, and B of a color filter are brought into contact with a machine platen 22, and are pressed with a press roller 23 placed on the reverse side of a glass substrate 21. Further, these publications disclose a method of applying, between the machine platen 22 and color ink layers, a film not liable to stick thereto or a releasing agent, and a method of rotating and moving the press roller 23.